A 14 kbp DNA fragment of an oncogene present in HT-1080 cells, a cell line derived from a human fibrosarcoma, has been cloned from DNA isolated from HT-1080-derived transformants utilizing lambda-1059 as the cloning vector. The human origin of the cloned DNA was demonstrated by the presence of human Alu repetitive sequences and by its poor hybridization to mouse cellular DNA. The cloned fragment was found to be present in all tested transfectants derived from HT-1080. The cloned oncogene fragment was found not to be related to either the T24 bladder carcinoma oncogene or to a number of retroviral onc genes.